Valve operating mechanism



Aug. 26, 1969 J. w. DOLBY VALVE OPERATING MECHANISM Filed March 12, 1968 yur s l Y me E wa. N M0 m W7 n N. A M Wm d United States Patent O 3,463,131 VALVE OPERATING MECHANISM John w. Dolby, 717 Douglas, Elgin, nl. 60120 Filed Mar. 12, 1968, Ser. No. 712,547 Int. Cl. F011 1/00 U.S. Cl. T23-90 3 Claims ABSTRACT OF THE DISCLOSURE A valve operating mechanism for use in an internal combustion engine utilizing a rocker arm for actuating the valve, a cam for opening the valve, and a second cam for closing the valve. The rocker arm is Pivoted on a bearing carried by the piston of a first hydraulic cylinder and held on the pivot by a retainer carried by the piston of a second hydraulic cylinder of smaller diameter than the iirst cylinder, whereby the center of the pivot is movable between the two hydraulic cylinders.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to mechanism adapted to open and close the intake and exhaust valves of internal combustion engines, particularly the higher performance engines.

Description of the prior art There have been many different mechanisms employed to open and close the intake and exhaust valves of internal combustion engines. There have been numerous improvements in these mechanisms seeking to accelerate the opening and closing action and to decrease the possibility of part failure.

The most common mechanism employed for actuating these valves employs a pivoted rocker arm having a tappet on one end to engage the valve stem and a follower on the other end to engage a cam to cause the valve to open. The valve is closed by the action of one or more springs. The springs are compressed during the opening of the valve and close the valve when the cam permits. This mechanism is very noisy and uses a significant portion of the power of the engine in repeatedly compressing the valve springs. These springs may break at high engine speeds and at times will break the valves themselves because they seat the valves with substantial force.

An improvement of the above mechanism employs hydraulic valve lifters to open the valves and springs to close them. The disadvantages of this mechanism include the problems of spring and valve breakage. There is a further disadvantage in connection with the hydraulic lifter. The hydraulic lifters must unload before the springs will close the valves. It has been found ditcult to unload the lifters fast enough to obtain proper valve seating at relatively high engine speeds. This results in loss of power, burned and broken Valves.

A third mechanism employed to perform this function utilizes an additional cam to assist the springs in the closing of the valves. At high engine speed the cam follower operating on this additional cam cannot follow the cam, resulting in valve float. When the lifter cams are shaped to give proper movement, by overlapping the valve action, the engine will operate satisfactorily at high speed but is unsatisfactory at low speed because of the excessive overlap.

A more effective mechanism has recently been devised, and is known as the desmodromic mechanism. In this structure the valve stem is carried by a cage-like device in which are mounted two separate cam followers. The

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cage surrounds a portion of the camshaft having one cam for opening the valve and a second cam for closing the valve. The seating of the valve is cushioned by a small spring structure interposed between the valve stem and the cage. In this device the valves are set by grinding oi the end of the stem against which the valve opening cam follower rests. The grinding of the end of the valve stem and the performance of the cushioning spring structure are both critical in this particular mechanism.

Thus, the object of this invention is to provide a valveoperating mechanism in which the valve is positively opened and seated by cams, without employing valveclosing or cushioning springs.

Anothel object is to provide a valve-operating mechanism which automatically compensates for variations in length of the valve-stem by reason of heating thereof during operation of the engine.

Further objects and advantages of this invention will become apparent as the following description proceeds and the features of novelty which characterize this invention will be pointed out with particularity inthe claims annexed to and forming a part of this specification.

A preferred embodiment of the invention is shown in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a view in elevation, with some parts in section of the invention, with the valve in the closed position.

FIG. 2 is a view similar to FIG. l with the valve in the open position.

FIG. 3 is an exploded view of the parts making up the valve, including the connector ball and rocker arm, and

FIG. 4 is an end view of the rocker arm showing the slotted socket construction.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is shown the valve and valve-operating mechanism. The valve 10 has a head 12 and a stem 14. The stem 14 is slidably mounted in the usual guide 16 and and terminates in a threaded end 18 (FIG. 3). A ball-shaped.connector member 20 is threadedly attached to the stem 14 and is held in position by the lock-nut 22.

The rocker arm 30 is formed with a socket 32 at its one end to receive the connector 20. The socket 32 is cylindrical in shape and has a lower open slot 34 to receive the upper end of the valve stem 14 when the parts are assembled. The axis of the cylindrical socket 32 is canted upwardly with respect to the pivot point 36 of the rocker arm 30, to decrease friction by providing a camming action between the ball connector 20 and the inside of the socket 32.

The pivoting of the rocker arm 30 about the pivot point 36 is shown somewhat schematically because of the wide variety of mechanisms known to accomplish this purpose. The pivot member 38 is shown as a horizontal bar upon which is engaged a semi-cylindrical flange 40 formed as a part of the rocker arm 30.

A hydraulic cylinder 50 having a piston 52 is mounted on the engine structure. The pivot member 38 is carried by the piston 52. Means for supplying hydraulic iiuid under pressure to the cylinder 50` are shown schematically at 54. A second hydraulic cylinder 56 having a piston 58 is also mounted on the engine structure. Means for supplying hydraulic uid under pressure to the cylinder 56 are shown schematically a-t 60. A retainer member 62, shown as an arcuate flange, is carried by the piston 58 and functions to hold the rocker arm 30 in engagement with the pivot member 38 by reacting against the arcuate portion 64 of the rocker arm 30. A wide variety of friction-reducing bearings may be employed between the pivot member 38 and the ange 40, and between the flange 62 and the arcuate portion 64.

As is apparent from FIG. 1, though somewhat exaggerated, the diameter of cylinder 50 is greater than the diameter of the cylinder 56. The means 54 and 60 for supplying uid under pressure to these cylinders are connected to a common source, and supply equal pressures to the two cylinders. Because cylinder 50 is of a larger diameter than cylinder 56, the force tending to move the pivot member 38 toward the cylinder 56 is greater than the force tending to move the ange 62 toward the cylinder 50. This will cause the pivot member 38 to move in a direction to compensate for any increase in length of the valve stem 14.

The cylinders 50 and 56 lare both provided with check valves 65 in the supply lines 54 `and 60. The check valves 65 stabilize the joint operations of the cylinders 50A and 56 and prevent the cylinder 50 from overpowering the cylinder 56, especially during the time in which the valve is open. Cylinder 50 is provided with a small air leak passage 66 to bleed oi air from the hydraulic uid. Preferably the passage 66 terminates at its upper end on the upper side of the pivot member 38. Since the air leak passage -66 will bleed oi a certain amount of oil with the air, it will provide lubrication to the connection between the pivot member 38 and the liange 40. A similar small air leak passage 68 is provided in the upper end of the cylinder 56 vfor a similar purpose. If the passage 68 is directed toward the cams, the oil which liows through it will provide lubrication to the cams. The passages 66 and 68 should be small enough as not to interfere with the operation of the cylinders 50 and 56.

The remaining end of the rocker varm 30 is shown as carrying two cam followers to act with two cams. As shown, the two cams are on separate cam shafts which are geared together to remain in synchronism, but, with a proper design of followers, the two cams may lbe mounted on a single camshaft. The lower follower 70 is moved -by the lower cam 72 to open the valve 10, while the upper follower 74 is moved by the upper cam 76 to close the valve 10 and to keep it closed. The cams 72 and 76, as shown, rotate in opposite directions and hold the followers captive between them, thereby positively controlling the opening and closing ofthe valve 10.

Because of substantial dilerences in valve-opening and closing requirements between various engines, the configuration ofthe cams will vary between engines. However, each pair of cams should be designed so that the valve-opening cam complements the valve-closing cam.

While there has been shown and described a particular embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In mechanism for operating yan intake or exhaust valve of an internal combustion engine havin-g a rocker arm pivotally mounted to act against the stem of the valve to cause the valve to open, cam means adapted to actuate said rocker arm about its pivot whereby said valve is moved to its open position, and means for moving said valve to its closed position, the improvement comprising a iirst hydraulic cylinder, pivotal mounting means for said rocker arm supported by said cylinder and movable in a direction substantially parallel to the longitudinal axis of the valve stem, a second hydraulic cylinder having a smaller diameter than the diameter of said iirst cylinder, retainer means mounted on said second cylinder and positioned to retain said rocker arm in pivotal engagement with said pivotal mounting means and movable in a direction substantially parallel to the longitudinal axis of the valve stem, and means for supplying operating fluid to both of said cylinders at identical pressures.

2. A mounting for a cam-actuated rocker arm adapted to open and close an intake or exhaust valve in an internal combustion engine comprising a rst hydraulic cylinder supported on said engine, a pivot *member mounted on said first cylinder to support said rocker anm in its rocking motion, a second hydraulic cylinder supported on said engine, said second hydraulic cylinder having a smaller diameter than the diameter of said first cylinder, retainer means carried -by said second cylinder and positioned to hold said rocker arm in pivotal relationship on said pivot member during the rocking motion of said rocker arm, and means for supplying operating tluid to both of said cylinders at the same pressure.

3. Mechanism for opening and closing an intake or exhaust valve of an internal combustion engine comprising a valve having a stem, a rocker arm having a cam follower at one end, a first cam rotatably mounted and adapted to move the cam follower on said rocker arm in a direction to cause said valve to open, a second cam rotatably mounted and adapted to move the cam follower on said rocker arm in a direction to cause said valve to close, a first hydraulic cylinder mounted on said en-gine, a pivot member mounted on said cylinder and adapted to support said rocker arm for pivotal movement, a second hydraulic cylinder of a smaller diameter than said first cylinder and -mounted on said engine, a retainer member carried by said second cylinder and adapted to retain said rocker yarm for pivotal movement about said pivot member, means for supplying operating fluid to both of said cylinders at the same pressure in each, and means forming a oating connection between the stem of said valve and the end of the rocker arm opposite the cam follower.

References Cited UNITED STATES PATENTS 1,408,781 3/ 1922 Sewell. 1,541,081 `6/ 1925 Vareille. 1,937,932 12/ 1933 Woolman. 3,045,657 7/ 1962 Sampietro.

FOREIGN PATENTS 122,180 3 1920 Great Britain.

AL LAWRENCE SMITH, Primary Examiner U.S. Cl. X.R. 184-6 

